1. Field of the Invention
This invention relates to novel derivatives of N-(2,2,6,6-tetraalkyl-4-piperidinyl)amic acid hydrazides. These compounds are very efficient in the stabilization of polymeric systems which are subject to degradation upon exposure to heat and/or light.
Particularly, this invention is related to acyl, carbamoyl, thiocarbamoyl, alkoxycarbonyl, aryloxycarbonyl, aralkoxycarbonyl, cycloalkoxycarbonyl, aliphatic, alicyclic, araliphatic, aryl, 2-hydroxyalkyl, 2-hydroxycycloalkyl and hydrazone derivatives of N-(2,2,6,6-tetraalkyl-4-piperidinyl)amic acid hydrazides.
2. Description of the Prior Art
Derivatives of hindered amine light stabilizing-substituted hydrazides (HALS-substituted hydrazides) are disclosed in U.S. Pat. Nos. 4,145,512 and 4,178,279. These patents teach reacting hindered amine light stabilizers (HALS) containing carboxylic acid hydrazide groups with isocyanate groups of polyisocyanates or isocyanate prepolymers to obtain light stabilized polyurethanes. However, the HALS-hydrazides employed were not HALS-substituted amic acid hydrazides and therefore do not have the enhanced stabilizing effect of the novel derivatives of the present invention.
U.S. Pat. No. 4,336,183 discloses various HALS spiro compounds containing a hydrazide functionality. It also discloses various acyl derivatives of these hydrazides. However, none of the hydrazides are N-HALS-substituted amic acid hydrazides and consequently the derivatives do not fall under the scope of the present invention.
U.S. Pat. No. 4,983,738, assigned to the assignee of the present invention, disclose N-(2,2,6,6-tetraalkyl-4-piperidinyl)amic acid hydrazides from which the compounds of the present invention may be prepared. These compounds are efficient light stabilizers for polymeric systems; however, the disclosed compounds have some volatility limitations and can be extracted out of the polymers to some degree by water or aqueous solutions.
U.S. Pat. No. 4,824,884, assigned to the assignee of the present invention, discloses cyclic anhydride derivatives of N-(2,2,6,6-tetraalkyl-4-piperidinyl)amic acid hydrazides. These compounds are also efficient heat and light stabilizers for polymeric systems but do not fall under the scope of this invention.
Prior to the present invention, the results obtained with the known hindered amine light stabilizers have not been satisfactory with all types of manufactured articles, due to certain deficiencies in stabilization, compatibility, volatility, exudability or economics. Therefore, further improvement in the field of hindered amine light stabilizers is still desirable. The novel compounds of this invention address these shortcomings.